High Dose Rate Radiotherapy Systems and Targets

One or more example embodiments relate to targets and/or radiotherapy systems including the same.

External beam radiation therapy may be used in the treatment of various cancers and non-malignant conditions. Generally, ionizing radiation, including, for example, photons, e.g., X-rays, gamma rays, and charged particles, e.g., protons and electrons, is directed at an area of interest. In many cases, such ionizing radiation is generated by a linear accelerator or a cyclotron.

Ultra-high dose rate (UHDR) radiotherapy is an emerging radiotherapy regime that appears to reduce radiation-induced toxicities while maintaining a tumor response similar to that of more conventional radiotherapy regimes—known as FLASH effect. UHDR radiotherapy may be characterized as delivering a high radiation rate, e.g., greater than about 40 Grays (Gy) per second, that allows for a total radiotherapy treatment dose, or large fractions of a total radiation dose, to be delivered in parts of a second, compared to several minutes for conventional radiotherapy. For example, a conventional radiotherapy treatment may include a total dose of 2-25 grays (Gy) delivered at a rate of up to 0.4 Gy/s, requiring minutes of treatment time. In contrast, UHDR radiotherapy may deliver a similar total dose at a rate of 40 Gy/s, requiring a fraction of a second of treatment time.

However, generating such high dosage radiotherapy uses an increase in instantaneous dose rates of several orders of magnitude in comparison to conventional instantaneous dose rates. For example, an instantaneous dose rate of UHDR radiotherapy may be 100 times or more higher than an instantaneous dose rate used in conventional radiotherapy. For FLASH photon (X-ray) radiotherapy, this uses corresponding increases in the electron currents impacting an X-ray target.

The scope of protection sought for various example embodiments is set out by the independent claims. The example embodiments and/or features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments.

Independent of the grammatical term usage, individuals with male, female or other gender identities are included within the term.

According to at least one example embodiment, a radiotherapy system comprises an X-ray target assembly configured to convert an electron beam into an X-ray beam, the X-ray target assembly including a first target configured to disperse at least a portion of the electron beam, and a second target configured to convert the portion of the electron beam into the X-ray beam, a thickness of the second target being greater than a thickness of the first target.

According to at least one example embodiment, an X-ray target assembly is configured to convert an electron beam into an X-ray beam, the X-ray target assembly comprising a first target configured to disperse at least a portion of the electron beam; and a second target configured to convert the portion of the electron beam into the X-ray beam, a thickness of the second target being greater than a thickness of the first target.

According to at least one example embodiment, a radiotherapy system comprises an X-ray target assembly configured to convert an electron beam into an X-ray beam, the X-ray target assembly including a first means configured to disperse at least a portion of the electron beam, and a second means configured to convert the portion of the electron beam into the X-ray beam, a thickness of the second means being greater than a thickness of the first means.

It should be noted that these figures are intended to illustrate the general characteristics of methods, structure and/or materials utilized in certain example embodiments and to supplement the written description provided below. These drawings are not, however, to scale and may not precisely reflect the precise structural or performance characteristics of any given embodiment and should not be interpreted as defining or limiting the range of values or properties encompassed by example embodiments. The use of similar or identical reference numbers in the various drawings is intended to indicate the presence of a similar or identical element or feature.

Various example embodiments will now be described more fully with reference to the accompanying drawings in which some example embodiments are shown.

Detailed illustrative embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.

It should be understood that there is no intent to limit example embodiments to the particular forms disclosed. On the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of this disclosure. Like numbers refer to like elements throughout the description of the figures.

As discussed herein the terminology “one or more” and “at least one” may be used interchangeably.

It will be appreciated that a number of example embodiments may be used in combination.

Although one or more example embodiments may be discussed herein with regard to an embodiment of an X-ray target positioned in a treatment head of a radiotherapy system, it should be understood that example embodiments should not be limited to such examples. Rather, an X-ray target described may also be deployed as an accessory to the treatment head.

To produce photon Flash radiotherapy, a high current electron beam is converted to photons in a Bremsstrahlung target. Typical static tungsten targets are damaged by the heat generated by the increased beam current required to produce the dose rate of photons (e.g., 40 Gy/s). The thermal strain on the target is held to a manageable level to ensure the target can produce photons at ultra-high dose rates.

A number of solutions to lower the target thermal strain have been proposed. One option is to increase the beam energy which increases Bremsstrahlung production efficiency in the target, but also increases the shielding, power and cooling requirements for the linac. Alternatively, one could move the target so the electron beam impacts a different material volume of the target with each subsequent pulse.

Increasing an electron beam spot size on the target improves heat dissipation and reduces thermal strain on the target. A measure to do this would allow for a smaller beam spot size at the target at, e.g., lower dose rates and/or higher energies, where a target can produce sufficient output without sacrificing the x-ray target life span, but also enlarge the beam spot size easily where used for lower energy and/or higher dose rate beams.

The inventors have discovered a thin target or foil, or series of thin targets or foils upstream of the main, thicker target would allow for an increased electron beam spot size for higher dose rate beams. These thin targets may completely cover the electron beam or be a series of shaped metal, wires, or slits to enable arbitrary beam shaping without or supplemented by a downstream multi-leaf collimator.

1 FIG. illustrates a block diagram of a radiation treatment system in accordance with example embodiments.

1 FIG. 100 100 illustrates a block diagram of an exemplary radiation treatment systemthat may serve as a platform for example embodiments. Radiation treatment systemmay be similar to a TrueBeam® radiotherapy system, commercially available from Varian Medical Systems, Palo Alto, CA.

10 20 30 30 20 10 18 100 A standsupports a rotatable gantrywith a treatment head. The treatment headmay extend into the gantry. In proximity to the standthere is arranged a control unitwhich includes control circuitry for controlling the different modes of operation of the system.

100 40 20 100 35 The radiation treatment systemcomprises a linear accelerator (linac), for example, within the gantry, utilized to create a radiation beam. Typically, the radiation treatment systemis capable of generating either an electron (particle) beam or an X-ray (photon) beam for use in the radiotherapy treatment of patients on a treatment couch. Other radiation treatment systems are capable of generating light ion particles such as protons, alpha particles, or carbon ions. For purposes of the following disclosure, only X-ray (photon) irradiation will be discussed.

20 40 45 45 47 45 49 45 45 52 50 45 55 52 50 50 50 50 50 50 A high voltage source is provided within the stand and/or in the gantry to supply voltage to an electron gun (not shown) positioned on an accelerator guide located in the gantry. Electrons are emitted from the electron gun into the acceleratorwhere they are accelerated. A source supplies radio frequency (microwave) power for the generation of an electric field within the waveguide. The electrons emitted from the electron gun are accelerated in the waveguide by the electric field, and exit the waveguide as a high-energy electron beam, for example, at megavoltage energies. The electron beammay pass through a set of bending plane scan magnets, in some embodiments. The electron beammay pass through a set of bend magnets, to redirect the electron beamfrom substantially horizontal to substantially vertical, in some embodiments. The electron beamthen enters a drift tubeand strikes a suitable X-ray target, for example, a Bremsstrahlung transmission target, converting a portion of the electron beaminto X-rays (photons)in the direction of a patient P. The drift tubereduces scattering before striking the targetand effectively reduces a source to surface distance (SSD) between a treatment surface and the target. The SSD may be measured from a top of the target, a middle of the target, a bottom of the targetor any other location in the target.

1 FIG. 35 30 104 116 20 116 50 178 20 116 178 20 122 178 30 As illustrated in, a patient P is shown lying on the treatment couch. High energy photons as described above are emitted from the treatment headin a divergent beam. Typically, a patient plane, is positioned, for example, about one meter from the X-ray source, and the rotational axis of the gantryis located on the patient plane, such that the distance between the targetand the isocenterremains constant when the gantryis rotated. It is appreciated that for photon FLASH therapy, the patient planemay be less than one meter from the electron source. The isocenteris at the intersection between the axis of rotation of the gantryand the central axis of beam. A treatment volume to be irradiated may be located about the isocenter, or in some embodiments may be located closer to or farther from the treatment head. It is appreciated that some treatment plans may utilize a primary treatment target that is off of the central beam axis, and such arrangements are within the scope of example embodiments.

2 FIG. 200 100 200 50 45 201 45 50 210 illustrates a side-sectional schematic representation of an exemplary beam pathwithin the radiation treatment system, in accordance with example embodiments. It is appreciated that the illustrated components of the beam pathare exemplary, and all may not be required in some embodiments. Additional components, e.g., a flattening filter (not shown), may also be included in accordance with embodiments of the present invention. Prior to impinging the X-ray target, the electron beammay pass through a set of cross plane scanning magnets, in some embodiments. As previously presented, the electron beamimpinges on the X-ray targetproducing the X-ray radiation beam.

210 250 250 260 270 210 The radiation beampasses through a monitor chamber, sometimes known or referred to as an “ion chamber.” The monitor chamberfunctions to measure a radiotherapy dose. X and Y jaws, and leaves of a multi-leaf collimator (MLC)function to shape radiation beamto a desired shape and/or beam profile for patient treatment. In addition or alternatively, as will be described in more detail below, a thin target may be used to modify the electron beam spot and also the distribution of the fluence of electrons within that spot.

220 220 30 260 116 270 30 1 FIG. 1 FIG. A primary collimatormay comprise a plurality of selectable collimators and/or filters, in some embodiments. The primary collimator, typically comprises an X-ray blocking material, and may be positioned in the head() to define the width of the X-ray beam at the patient plane. Typically, the X and Y jawsare moveable and, when fully open, define a maximum beam width at the patient plane(). The MLCmay be positioned at the exit of the head, to further shape the X-ray beam. Exemplary MLCs may use up to 120 individually controllable leaves, for example, thin slices of tungsten, which may be moved into or out of the X-ray beam under the control of system software.

As a high-energy electron beam, e.g., 22 MeV passes through an X-ray target, e.g., Tungsten (W) or Tantalum (Ta), the linear energy transfer (LET) dictates the heat generation profile within the target. LET refers to the energy that an ionizing particle transfers to the material per unit distance traveled. In some example embodiments, the X-ray target may include at least two materials, e.g., Tungsten and copper or Tantalum and copper. As the electron beam penetrates deeper into the target material, the LET gradually increases, reaching a maximum at a critical thickness. Beyond this critical thickness, the stopping power becomes excessively high, leading to a rapid absorption of beam energy. For 22 MeV for example, the critical thickness for W/Ta is approximately 1.15 mm.

50 50 The X-ray targetis designed to include multiple layers of spatially separated targets ensuring (i) heat dissipation for a beam incident on a thicker target and ii) >99% of the incident electrons lose all of their energy (are absorbed) in the X-ray target.

50 50 50 In accordance with example embodiments, the X-ray targetis configured to operate in UHDR radiotherapy and absorb >99% of the incident electrons. In accordance with other example embodiments, the X-ray targetis also configured to operate in ultra-high dose rate (UHDR) radiotherapy, e.g., at least 1 Gray (Gy) per second and absorb >99% of the incident electrons. Additionally or alternatively, the X-ray targetis configured to operate with conventional dose rate beams (e.g., <0.40 Gy/s).

3 FIG. illustrates a side view of an X-ray target according to one or more example embodiments.

3 FIG. 50 350 1 350 2 350 1 350 2 45 210 350 1 As shown in, the X-ray targetincludes two target layers-to-. Each of the plurality of target layers-to-is configured to convert a portion of the electron beaminto a portion of the radiation beam. While only two layers are shown, it should be understood that the target layer-may be divided into a plurality of target layers.

350 1 350 2 2 350 2 350 1 350 1 45 350 1 350 2 350 2 45 104 350 2 350 2 The target layer-(a first target) may be a thin target and the target layer-(a second target) may be a thick target (i.e., a thickness TH-of the target layer-is larger than a thickness TH-1 of the target layer-). The target layer-can act as a scattering foil and is configured to disperse at least a portion of the electron beam. The thin target layer-spreads out the electron beam spot for better heat dissipation when it impacts the thick target layer-. The thick target layer-is configured to convert the portion of the electron beaminto the X-ray beam. In some example embodiments, the thick target layer-is thick enough to absorb at least 99% of electrons of the electron beam incident on the thick target layer-(e.g., all electrons).

1 350 1 350 2 The thickness TH-of the target layer-, composition and position relative to the target layer-(e.g., the Bremsstrahlung) can be optimized to produce the desired beam spot.

350 1 350 2 122 350 1 350 2 In some example embodiments, the plurality of target layers-to-are stacked in series, e.g., along the central axis of the beam. However, example embodiments are not limited thereto. Moreover, the plurality of target layers-to-may be separated by a constant distance or an adjustable distance.

350 1 350 1 In some example embodiments, the target layer-may be a foil or plate and include brass. In some example embodiments, the thickness TH-1 of the target layer-is less than 1 cm and may be constant.

350 1 350 1 350 2 350 1 350 1 350 1 If changes in beam spot shape are desired, the target layer-, may be shaped to, e.g., scatter only part of the electron beam or as a series of slits to optimize beam spot shape. The electron beam at the target layer-is smaller than the beam at layer target-because the target layer-will spread the electron beam out. The target layer-may be a foil, covering the whole electron beam, and in other example embodiments the first target-is, e.g., a wire configured to spread the electron beam in one dimension only.

350 1 350 1 350 2 350 1 350 2 350 1 In other example embodiments, the target layer-may be a foil or plate with a variable thickness. With a variable thickness, the target layer-produces a beam spot with a desired shape on the target layer-. A penumbra (a fall off at an edge of the electron beam) depends on the spot size and shape of the beam. Using the target layer-allows refinement of the penumbra and beam shaping. For Flash beams, the beam spot may be larger for heat dissipation in the target layer-. Thus, in some example embodiments for Flash beams, the target layer-may be designed to be a particular shape to reduce the impact of the larger spot size on patient treatment plans.

The desired shape may be a 2D electron beam pattern.

350 1 In other example embodiments, the target layer-may be a wire or a set of wires instead of a plate or foil.

350 2 350 1 350 2 The target layers-may comprise at least one refractory metal. Refractory metals are characterized as a high Z materials, e.g., materials comprising elements with a high atomic number (“Z”) of protons in the nucleus, and having a high melting temperature. As used herein, “high-Z” refers to or describes elements having an atomic number of 42, corresponding to molybdenum (Mo), or greater. Exemplary elements include tungsten (W), tantalum (Ta), molybdenum (Mo), gold (Au), and/or antimony (Sb). The total thickness of the target layers-to-is selected to be sufficient to generate the required dose of X-rays, while minimizing attenuation and energy loss of the incident high-energy electrons.

4 FIG.A 4 4 FIGS.B-E illustrates a target and corresponding electron beam spot.illustrate target assemblies and corresponding electron beam spots according to one or more example embodiments.

4 FIG.A 4 4 FIGS.A-E 350 45 350 350 1 405 350 350 a illustrates a targetas a single layer. As shown, the electron beamstrikes the targetwithout any intermediary layer. Due to the absence of an intermediary layer (e.g., the first target layer-), a concentrated beam spotoccurs on the target. As described above, heat dissipation is reduced and reduce thermal strain on the targetis increased relative to using an intermediary target layer. In, a darker shade in a particular beam spot reflects an increased number of electrons striking the target relative to a lighter shade in the particular beam spot.

4 FIG.B 4 FIG.B 3 FIG. 4 FIG.B 350 1 350 2 350 1 45 350 1 350 1 45 350 2 405 405 405 350 2 a a a a a b b a illustrates the target assembly includes two target layers-and-. The target assembly shown inmay be the same as the target assembly shown in. The target layer-may be a rectangular thin foil target. As shown in, the electron beamstrikes the target layer-, which causes the electron beam to spread out in all directions of two dimensions defined by the length and width of the of target layer-. This results in an electron beamthat hits the target layer-and forming a beam spot. As shown, the beam spotis spread out in a radial direction relative to the beam spot, resulting in improved heat dissipation and reduced thermal strain on the target layer-.

4 FIG.C 4 FIG.C 350 1 350 2 350 1 45 350 1 350 1 45 350 2 405 405 350 1 405 350 2 b b b b b c c b a illustrates the target assembly includes two target layers-and-. The target layer-may be a target in the shape of a wire. As shown in, the electron beamstrikes the target layer-, which causes the electron beam to spread out, primarily along the longitudinal axis of the target layer-. This results in an electron beamthat hits the target layer-and forming a beam spot. As shown, the beam spotis spread out along the longitudinal axis of the target layer-relative to the beam spot, resulting in improved heat dissipation and reduced thermal strain on the target layer-.

4 FIG.D 4 FIG.D 350 1 350 2 350 1 450 45 350 1 350 1 45 350 2 405 405 405 350 2 45 350 1 350 2 405 450 405 c c c c c d d a d d illustrates the target assembly includes two target layers-and-. The target layer-may be a target having three overlapping triangular foils. As shown in, the electron beamstrikes the target layer-, which causes the electron beam to spread out based on the shape of the target layer-. This results in an electron beamthat hits the target layer-and forming a beam spot. As shown, the beam spotis spread out relative to the beam spot, resulting in improved heat dissipation and reduced thermal strain on the target layer-. Beamlets within the electron beamare spread and energy attenuated based on the thickness and composition of the target layer-they interact with, resulting in a complex patter of electron beam spot shape and fluence on the thick target-. Moreover, areas of the beam spotthat correspond the overlapping portions of the triangular foilsare impacted by a lower number of electrons than the areas of the beam spotthat do not correspond to the overlapping portions.

4 FIG.E 4 FIG.E 350 1 350 2 350 1 2 350 1 45 350 1 350 1 45 350 2 405 405 405 350 2 405 405 d d d d d d e e a e e illustrates the target assembly includes two target layers-and-. The target layer-may be a rectangular thin foil target withslits across a width of the target layer-. As shown in, the electron beamstrikes the target layer-, which causes the electron beam to spread out based on the shape of the target layer-. In addition, due to the slots, electrons are not dispersed if they pass through one of the two slits. This results in an electron beamthat hits the target layer-and forming a beam spot. As shown, the beam spotis spread out relative to the beam spot, resulting in improved heat dissipation and reduced thermal strain on the target layer-. Moreover, areas of the beam spotthat correspond the slots are impacted by a higher number of electrons than the areas of the beam spotthat do not correspond to the slots.

350 1 350 2 4 4 FIGS.B-E It should be understood that the target layer-is not limited to the shapes shown inand other shapes may be used to create a desired beam spot on the target layer-.

3 FIG. 350 1 350 50 350 1 350 n n Referring back to, in some example embodiments, each of the target layers-to-is 0.1 mm for an X-ray targetcomprising Tantalum (Ta) or Tungsten (W). In some example embodiments, each of the target layers-to-may be the same material.

350 2 50 In some example embodiments, the thickness TH-2 of the target layer-may be the same thickness as a single piece target such as 1 mm for an X-ray targetcomprising Ta.

For example, an exemplary UHDR radiotherapy treatment may use an electron energy of at least 50 MeV, producing up to 25 kW of average beam power.

50 350 1 350 2 350 2 As attenuation of high-energy electrons within the X-ray targetproduces heat, the target layer-spreads out the electron beam spot for better heat dissipation when it impacts the target layer-. Reducing heating of the target layer-improves the stability and reliability of a UHDR radiotherapy system.

350 1 350 2 350 2 50 350 1 350 2 350 2 350 2 The spacing of the target layers-to-in series along the electron beam path allows for heat management through at least one of heat sinks, air cooling, radiative transfer, or (high-pressure) water cooling and an increased beam spot size on the target layer-. For example, the targetmay be used with the cooling system described in U.S. Pat. No. 8,761,347, the entire contents of which are incorporated by reference. The spacing of the target layer-to-can be paired with existing heat management solutions involving a moving target or scanning beam such as described in U.S. Pat. No. 12,186,587, the entire contents of which are incorporated by reference. Moreover, by maintaining the thickness of the target layer-to be the same as a single piece target, the electrons are stopped within the target layer-, resulting in no need for additional electron contamination management.

5 FIG.A 500 500 500 502 504 506 508 504 506 50 504 506 504 508 510 502 is a perspective view of an exemplary target assemblyin accordance with some example embodiments. The target assemblypositions a target in the beam path for generation of X-rays in a photon mode, or moves a target out of the beam path in an electron mode. The target assemblyincludes a channel mount, a substratesupporting one or more target buttonsand a cooling tubecoupled to the substratefor supplying a cooling fluid. At least one of the one or more target buttonsmay be the target. Channels can be provided in the substrateadjacent or surrounding the target buttonsfor circulating a cooling fluid to dissipate heat generated during target operation. The substrateand the cooling tubecan be supported by a mount assembly, which is movable relative to the channel mount.

500 508 The target assemblyand cooling tubeare further described in U.S. Pat. No. 8,761,347, the entire contents of which are incorporated by reference.

50 Thus, the targetmay be used with existing cooling mechanisms.

5 5 FIGS.B-C 5 FIG.B 5 5 FIGS.B-C 50 508 1 508 2 350 1 350 2 illustrate at least one example embodiment using a plurality of cooling tubes.illustrates a cross-sectional view of the target assembly. In some example embodiments, a plurality of cooling tubes-and-may be used for the target layers-and-, respectively, as shown in.

5 FIG.B 350 1 350 2 504 1 504 504 1 504 520 350 504 1 504 n n n. As shown in, each of the target layers-to-is placed in a corresponding heat sink layer-to-. More specifically, each heat sink layer-to-has a receiving areawith a diameter that is the same or slightly larger than the target layercorresponding to the heat sink layer-to-

508 Each of the layers includes a cooling tube.

500 45 The target assemblymay include a plurality of slots to accommodate a varying number of target layers. For example, the target assembly may have n slots and n cooling tubes. Based on the energy level of the beam, a selected number of target and heat sink layers may be inserted into the n slots. The selected number may be n or less than n. Each of the slots may have a defined mounting for a target and heat sink layer. Moreover, while the combination of a layer is described as a target and heat sink layer, it should be understood that the slots may accommodate a combination target layer and heat transfer material layer and/or a combination of the target layer, heat transfer material layer and heat sink layer.

5 FIG.C illustrates a top view (e.g., beam-eye view) of the first layer. The remaining layers are the same, with the exception of the size of the target layer within the corresponding layer.

5 FIG.C 508 1 550 530 550 530 504 1 550 555 550 350 1 550 As shown in, the cooling tube-supplies water (or another cooling liquid) to a cooling channelthrough a coupling. The cooling channeland the couplingmay be embedded in the heat sink layer-. The cooling channelmay have a general u-shape. A curved portionof the U-shaped cooling channelmay have a curvature that matches the curvature of the target layer-. However, example embodiments are not limited thereto and the cooling channelmay have a different shape.

530 Moreover, each of the couplingsmay include valve that is operable based on whether a target and heat sink layer is being used in a slot. For example, if a target and heat sink layer is present in the slot, the valve is open to allow the flow of water through a channel in the heat sink layer. If no target and heat sink layer is present in the slot, the corresponding valve is closed.

350 2 350 1 350 1 In other example embodiments, the cooling system may be provided for the thicker target layer-and not the layer-. In the thin target-, there is less heat deposited so a cooling system may not be used.

5 FIG.A 500 514 514 514 514 a b c Referring back to, the target assemblycan be moved by a linear axis, which includes a motor, a ball screw, a couplercoupling the motor and the ball screw, and a ball nutengaging the ball screw.

500 500 506 506 506 500 514 506 514 506 a b c The target assemblymay include one or more targets each being optimized to match the energy of an incident electron beam. For example, the target assemblymay include a first targetadapted for a first photon mode, a second targetfor a second photon mode and a third targetfor a third photon mode. It should be noted that a different number of targets may be included in the target assembly. In operation, the linear axismoves or positions one of the targetsin the beam path for a photon mode. In an electron mode, the linear axisremoves the targetsout of the beam path to allow an electron beam passes unimpeded.

500 514 506 514 506 It should be noted that a different number of targets may be included in the target assembly. In operation, the linear axismoves or positions one of the targetsin the beam path for a photon mode. In an electron mode, the linear axisremoves the targetsout of the beam path to allow an electron beam passes unimpeded.

6 FIG. illustrates a block diagram of a control system with which embodiments may be implemented.

600 18 600 6 FIG. In some embodiments, a control systemshown inmay be used to implement the control unit. The control systemmay also be an example of any control system described herein.

600 602 604 602 604 600 606 602 604 106 604 600 608 602 604 610 602 The control systemincludes a busor other communication mechanism for communicating information, and processing circuitry(e.g., at least one processor and/or ASIC) coupled with the busfor processing information. In examples where the processing circuitryis hardware configured to executed stored instructions (e.g., a processor), the control systemalso includes a main memory, such as a random-access memory (RAM) or other dynamic storage device, coupled to the busfor storing information and instructions to be executed by the processing circuitry. The main memoryalso may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processing circuitry. The control systemfurther includes a read only memory (ROM)or other static storage device coupled to the busfor storing static information and instructions for the processing circuitry. A data storage device, such as a magnetic disk or optical disk, may be provided and coupled to the busfor storing information and instructions.

600 602 612 614 602 604 616 604 612 The control systemmay be coupled via the busto a display, such as a flat panel, for displaying information to a user. An input/output device, such as a touchscreen, is coupled to the busfor communicating information and command selections to processing circuitry. Another type of user input device is cursor control, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processing circuitryand for controlling cursor movement on display. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane.

612 614 600 612 614 600 612 614 616 While the displayand I/O deviceare shown outside of the control system, it should be understood that the displayand the I/O deviceare part of the control system. Moreover, while the display, the I/O deviceand the curser controlare illustrated as separate components, it should be understood that they may be combined, such as a touch screen display.

600 600 604 606 606 610 606 604 606 In some embodiments, the control systemcan be used to perform various functions described herein. According to some embodiments, such use is provided by control systemin response to the processing circuitryexecuting one or more sequences of one or more instructions contained in the main memory. Those skilled in the art will know how to prepare such instructions based on the functions, algorithms and methods described herein. Such instructions may be read into the main memoryfrom another processor-readable medium, such as storage device. Execution of the sequences of instructions contained in the main memorycauses the processing circuitryto perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in the main memory. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the various embodiments described herein. Thus, embodiments are not limited to any specific combination of hardware circuitry and software.

602 Transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise the bus. Transmission media can also take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications.

604 600 1602 602 606 604 606 610 604 Various forms of processor-readable media may be involved in carrying one or more sequences of one or more instructions to the processing circuitryfor execution. For example, the instructions may initially be carried on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a network, such as the Internet or a local network. A receiving unit local to the control systemcan receive the data from the network and provide the data on the bus. The buscarries the data to the main memory, from which the processing circuitryretrieves and executes the instructions. The instructions received by the main memorymay optionally be stored on the storage deviceeither before or after execution by the processing circuitry.

600 618 602 618 620 622 618 618 618 The control systemalso includes a communication interfacecoupled to the bus. The communication interfaceprovides a two-way data communication coupling to a network linkthat is connected to a local network. For example, the communication interfacemay be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, the communication interfacemay be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, the communication interfacesends and receives electrical, electromagnetic or optical signals that carry data streams representing various types of information.

620 620 622 624 626 620 620 618 600 600 620 618 The network linktypically provides data communication through one or more networks to other devices. For example, the network linkmay provide a connection through local networkto a host computeror to equipmentsuch as a radiation beam source or a switch operatively coupled to a radiation beam source. The data streams transported over the network linkcan comprise electrical, electromagnetic or optical signals. The signals through the various networks and the signals on the network linkand through the communication interface, which carry data to and from the control system, are exemplary forms of carrier waves transporting the information. The control systemcan send messages and receive data, including program code, through the network(s), the network link, and the communication interface.

Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of this disclosure. As used herein, the term “and/or,” includes any and all combinations of one or more of the associated listed items.

When an element is referred to as being “connected,” or “coupled,” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. By contrast, when an element is referred to as being “directly connected,” or “directly coupled,” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between,” versus “directly between,” “adjacent,” versus “directly adjacent,” etc.).

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.

Specific details are provided in the following description to provide a thorough understanding of example embodiments. However, it will be understood by one of ordinary skill in the art that example embodiments may be practiced without these specific details. For example, systems may be shown in block diagrams so as not to obscure the example embodiments in unnecessary detail. In other instances, well-known processes, structures and techniques may be shown without unnecessary detail in order to avoid obscuring example embodiments.

As discussed herein, illustrative embodiments are described with reference to acts and symbolic representations of operations (e.g., in the form of flow charts, flow diagrams, data flow diagrams, structure diagrams, block diagrams, etc.) that may be implemented as program modules or functional processes include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types and may be implemented using existing hardware, for example, processing or control circuitry such as, but not limited to, one or more processors, one or more Central Processing Units (CPUs), one or more controllers, one or more arithmetic logic units (ALUs), one or more digital signal processors (DSPs), one or more microcomputers, one or more field programmable gate arrays (FPGAs), one or more System-on-Chips (SoCs), one or more programmable logic units (PLUs), one or more microprocessors, one or more Application Specific Integrated Circuits (ASICs), or any other device or devices capable of responding to and executing instructions in a defined manner.

Although a flow chart may describe the operations as a sequential process, many of the operations may be performed in parallel, concurrently or simultaneously. In addition, the order of the operations may be re-arranged. A process may be terminated when its operations are completed, but may also have additional steps not included in the figure. A process may correspond to a method, function, procedure, subroutine, subprogram, etc. When a process corresponds to a function, its termination may correspond to a return of the function to the calling function or the main function.

As disclosed herein, the term “memory,” “storage medium,” “processor readable medium,” “computer readable storage medium” or “non-transitory computer readable storage medium” may represent one or more devices for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other tangible machine-readable mediums for storing information. The term “computer-readable medium” may include, but is not limited to, portable or fixed storage devices, optical storage devices, and various other mediums capable of storing, containing or carrying instruction(s) and/or data.

Furthermore, example embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine or computer readable medium such as a computer readable storage medium. When implemented in software, a processor or processors will perform the necessary tasks. For example, as mentioned above, according to one or more example embodiments, at least one memory may include or store computer program code, and the at least one memory and the computer program code may be configured to, with at least one processor, cause a network element or network device to perform the necessary tasks. Additionally, the processor, memory and example algorithms, encoded as computer program code, serve as means for providing or causing performance of operations discussed herein.

The terms “including” and/or “having,” as used herein, are defined as comprising (i.e., open language). The term “coupled,” as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. Terminology derived from the word “indicating” (e.g., “indicates” and “indication”) is intended to encompass all the various techniques available for communicating or referencing the object/information being indicated. Some, but not all, examples of techniques available for communicating or referencing the object/information being indicated include the conveyance of the object/information being indicated, the conveyance of an identifier of the object/information being indicated, the conveyance of information used to generate the object/information being indicated, the conveyance of some part or portion of the object/information being indicated, the conveyance of some derivation of the object/information being indicated, and the conveyance of some symbol representing the object/information being indicated.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause or result in such benefits, advantages, or solutions, or cause such benefits, advantages, or solutions to become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims.

Illustrative embodiment 1 includes a radiotherapy system comprising an X-ray target assembly configured to convert an electron beam into an X-ray beam, the X-ray target assembly including a first target configured to disperse at least a portion of the electron beam, and a second target configured to convert the portion of the electron beam into the X-ray beam, a thickness of the second target being greater than a thickness of the first target.

Illustrative embodiment 2 includes the radiotherapy system of illustrative embodiment 1, wherein the radiotherapy system is configured to control the electron beam such that the X-ray beam delivers a radiation rate of at least 40 grays per second (Gy/s).

Illustrative embodiment 3 includes the radiotherapy system of any one of illustrative embodiments 1, wherein the radiotherapy system is configured to control the electron beam such that the X-ray beam delivers a radiation rate of less than 40 grays per second (Gy/s).

Illustrative embodiment 4 includes the radiotherapy system of any one of illustrative embodiments 1-3, wherein the first target and the second target are stacked in series.

Illustrative embodiment 5 includes the radiotherapy system of any one of illustrative embodiments 1-4, wherein the first target includes a plurality of slits.

Illustrative embodiment 6 includes the radiotherapy system of any one of illustrative embodiments 1-5, wherein the first target is rectangular.

Illustrative embodiment 7 includes the radiotherapy system of any one of illustrative embodiments 1-6, wherein the first target is a wire or a plurality of wires.

Illustrative embodiment 8 includes the radiotherapy system of any one of illustrative embodiments 1-6, wherein the first target is a foil.

Illustrative embodiment 9 includes the radiotherapy system of any one of illustrative embodiments 1-8, wherein the first target includes brass.

Illustrative embodiment 10 includes the radiotherapy system of any one of illustrative embodiments 1-9, wherein the second target includes at least one of tantalum (Ta) or tungsten (W).

Illustrative embodiment 11 includes the radiotherapy system of illustrative embodiment 8, wherein the foil includes overlapping layers of the foil.

Illustrative embodiment 12 includes the radiotherapy system of illustrative embodiment 11, wherein the layers are triangular.

Illustrative embodiment 13 includes the radiotherapy system of any one of illustrative embodiments 1-12, wherein the thickness of the first target is less than 1 cm.

Illustrative embodiment 14 includes the radiotherapy system of any one of illustrative embodiments 1-13, wherein the thickness of the first target varies.

Illustrative embodiment 15 includes the radiotherapy system of any one of illustrative embodiments 1-14, further comprising at least one cooling apparatus coupled to the second target and configured to supply a cooling fluid to the second target.

Illustrative embodiment 16 includes the radiotherapy system of any one of illustrative embodiments 1-15, wherein the X-ray target assembly is configured to absorb at least 99% of electrons of the electron beam, the electron beam incident on the first target.

Illustrative embodiment 17 includes the radiotherapy system of any one of illustrative embodiments 1-16, wherein the second target is configured to absorb at least 90% of electrons of the dispersed electron beam.

Illustrative embodiment 18 includes an X-ray target assembly configured to convert an electron beam into an X-ray beam, the X-ray target assembly comprising a first target configured to disperse at least a portion of the electron beam; and a second target configured to convert the portion of the electron beam into the X-ray beam, a thickness of the second target being greater than a thickness of the first target.

Illustrative embodiment 19 includes the X-ray target assembly of illustrative embodiment 18, wherein the first target and the second target are stacked in series.

Illustrative embodiment 20 includes the X-ray target assembly of any one of illustrative embodiments 18-19, wherein the first target is a foil.